plant molecular biologist
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Despite cautions from their conservative elders, young chemists like Paternó and van't Hoff began interpreting molecular graphs in terms of the arrangement of a molecule's atoms in 3-dimensional space. Benzene was one such case, but still more significant was the prediction, based on puzzling isomerism involving "optical activity," that molecules could be "chiral," that is, right- or left-handed. Louis Pasteur effected the first artificial...more
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We can use methods of genetic analysis to connect phylogenic information to geographical histories. Human migration has left genetic traces on every continent, and allows us to trace our roots back to Africa. Molecular genetic methods allow us to determine whether or not trait states were ancestral, which can have profound implications for fundamental biological ideas.
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Wirt explains that the invention of the electric motor revolutionized the way factories operate. With steam power, there was one central boiler which dictated how the factory had to be organized. As electric motors evolved, it became possible to make small motors that could be distributed around the plant to provide power to individual machines allowing for greater flexibility. Now, electric motors are everywhere, he says....more
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The lecture opens with tricks ("Z-effective" and "Self Consistent Field") that allow one to correct approximately for the error in using orbitals that is due to electron repulsion. This error is hidden by naming it "correlation energy." Professor McBride introduces molecules by modifying J.J. Thomson's Plum-Pudding model of the atom to rationalize the form of molecular orbitals. There is a close analogy in form between the molecular orbita...more
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This lecture begins by applying the united-atom "plum-pudding" view of molecular orbitals, introduced in the previous lecture, to more complex molecules. It then introduces the more utilitarian concept of localized pairwise bonding between atoms. Formulating an atom-pair molecular orbital as the sum of atomic orbitals creates an electron difference density through the cross product that enters upon squaring a sum. This "overlap" term is th...more
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Although molecular mechanics is imperfect, it is useful for discussing molecular structure and energy in terms of standard covalent bonds. Analysis of the Cambridge Structural Database shows that predicting bond distances to within 1% required detailed categorization of bond types. Early attempts to predict heats of combustion in terms of composition proved adequate for physiology, but not for chemistry. Group- or bond-additivity schemes a...more
